Photofragmentation dynamics of ICN^-(CO₂)_n clusters following visible excitation

Photodissociation of ICN^-(CO₂)_n, n = 0-18, with 500-nm excitation is investigated using a dual time-of-flight mass spectrometer. Photoabsorption to the ²Π_1/2 state is detected using ionic-photoproduct action spectroscopy; the maximum absorption occurs around 490 nm. Ionic-photoproduct distributions were determined for ICN^-(CO₂)_n at 500 nm. Following photodissociation of bare ICN^- via 430-650 nm excitation, a small fraction of CN^- is produced, suggesting that nonadiabatic effects play a role in the photodissociation of this simple anion. Electronic structure calculations, carried out at the MR-SO-CISD level of theory, were used to evaluate the potential-energy surfaces for the ground and excited states of ICN^-. Analysis of the electronic structure supports the presence of nonadiabatic effects in the photodissociation dynamics. For n ≥ 2, the major ionic photoproduct has a mass corresponding to either partially solvated CN ^- or partially solvated [NCCO₂]^-.